Fetch the first tab inside the browser startup retry loop.

content/test/gpu/gpu_tests/screenshot_sync_integration_test.py

 # Copyright 2017 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import logging
 import os
 import random
 
 from gpu_tests import gpu_integration_test
 from gpu_tests import path_util
@@ skipping 53 matching lines @@
 
   @classmethod
   def RestartBrowserIfNecessaryWithArgs(cls, browser_args):
     if not browser_args:
       browser_args = []
     if set(browser_args) != cls._last_launched_browser_args:
       logging.info('Restarting browser with arguments: ' + str(browser_args))
       cls.StopBrowser()
       cls.CustomizeBrowserArgs(browser_args)
       cls.StartBrowser()
-      cls.tab = cls.browser.tabs[0]
 
   @classmethod
   def _CreateExpectations(cls):
     return screenshot_sync_expectations.ScreenshotSyncExpectations()
 
   @classmethod
   def GenerateGpuTests(cls, options):
     yield('ScreenshotSync_SWRasterWithCanvas',
           'screenshot_sync_canvas.html',
           ('--disable-gpu-rasterization'))
@@ skipping 41 matching lines @@
       for x in range(start_x, outer_size, skip):
         self._CheckColorMatchAtLocation(canvasRGB, screenshot, x, y)
 
   def RunActualGpuTest(self, test_path, *args):
     browser_arg = args[0]
     self.RestartBrowserIfNecessaryWithArgs([browser_arg])
     self._Navigate(test_path)
     repetitions = 20
     for _ in range(0, repetitions):
       self._CheckScreenshot()